The visually evoked potential (VEP) generated by changing the luminance of a large unstructured field is a potentially useful way of assessing visual function because it can be applied to a wide variety of patients. The nonlinear properties of the VEP requires the use of a stimulus that is sufficiently general to adequately test the response characteristics. To this end we are using new stimuli which consist of pseudorandom periodic sequences. The power spectrum and the first and second cross-correlations of the VEP to such stimuli are being studied in both normal and abnormal subjects.